div {
  width: 500px;
  height: 500px;
  background-color: aqua;
}
div > div3 {
  width: 200px;
  height: 200px;
  background-color: blue;
}
div div1 {
  width: 400px;
  height: 400px;
  background-color: aquamarine;
}
div div1 div2 {
  width: 300px;
  height: 300px;
  background-color: bisque;
}
.box {
  width: 300px;
  height: 300px;
  background-color: blueviolet;
}
.box::before {
  content: '';
  display: block;
}
.box .box3 {
  width: 200px;
  height: 200px;
}
.box .box3:hover {
  color: red;
}
